Radiofrequency system



Nov. 17, 192 1 1,561,914 H. F. ELLIOTT ET AL RADIOFREQUENCY SYSTEM Filed Jan. 9, 1922 2 Sheets-Sheet l K5 X 1.17010 3 l 76 INVENTOIQS.

MM 224 34 ATTQRNEYS Nov. 17, 1925 1,561,914 H. F. ELLIOTT ET AL RADIOFREQUENCY SYSTEM Filed Jan. 9, 1922 2 Sheets-Sheet 2 WITNESS IN l ENTOR #EELL/orr 4nd JA/V/LLEa BYY Zai/ ATTORNEYS Patented Nov.. 17, 1925.

f UNITED STATES PATENT OFFICE.

HAROLD F. ELLIOTT AND JAMES ARTHUR MILLER, 01: PALO ALTO, CALIFORNIA, ASSIGNORS, BY MESNE ASSIGNMENTS, TO FEDERAL TELEGRAPH COMPANY, OF SAN FRANCISCO, CALIEORNIA, A CORPORATION OF CALIFORNIA. I

RADIOFREQUENCY SYSTEM.

Application filed January 9, 1922. Serial No. 527,884.

To all whom it may concern:

Be it known that we, HAROLD F. ELLIOTT and JAMns ARTHUR MILLER, citizens of the and residents of Palo Alto,

United States, in the county of Santa Clara and State of California, have invented a new and useful Ptadiofrequency System, of which the following is a specification.

Our invention relates to a radio frequency when the total load would be too large for one converter, again, when a plurality of arcs of low rating onlyv are available and it is desired to increase the output. The scheme may also be used to advantage in large radio stations in which there are a plurality of arc converters, each designed to communicate with a distant point, there being as many channels of communication as there are converters. By parallelinga plurality of the arcs, an increased power may be obtained, even though temporarily, with a correspondingly reduced number of channels of communication. The combined units may serve to transmit signals for extra long distances, or under severe conditions necessi-' tating greater power. In this way, the flexibility of such an installation can be materially increased. r

The parallel operation of arcs may be of further advantage in case they are fed from an alternating current source. If but one such arc is utilized, the amplitude of the current supplied to the oscillatory circuit varies through a regular cycle in accordance with the alternations of the supply voltage. By paralleling arcs fed from different phases of a polyphase system, the amplitude ofthe oscillations are made to be substantially uniform.

It has been found that the stability and steadiness'of operation of a plurality of arcs in parallel under different conditions are materially enhanced over the operation of a single radio frequency are converter.

Although these advantages, as well as others, are well known for the parallel operation of arcs, this mode of operation so as to render it satisfactory is ordinarily dlflicult of maintenance. This arises from the fact that certain conditions must be fulfilled in order that the operation in parallel may be desirable. The are converters must be kept in synchronism with respect to. their output radio frequency currents; they should divide the load between them in any predetermined manner, and their operation should be confined to a predetermined path .or frequency. It is one of the objects of our invention to insure the satisfactory operation of converters or other sources of oscillations in parallel.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at lengthin the following description, where there will be outlined in full those forms of the invention selected for illustration in thedrawings accompanying and forming part of the present specification. In the drawings, we have shown several embodiments of our invention, but it is "to be understood that we do not limit ourselves to such forms, since the invention as expressed in the claims may be embodied in a plurality of other forms' -Referring to the drawings,-

- Figure 1 is a wiring diagram of one form of ourinvention;

Fig. 2 is a wiring diagram of another,

form;

Figs. 3, 4, 5 and 6.show embodiments of the invention in systems using a polyphase low frequency source for the supply of power to the converter; and

Fig. 7 shows amodification of the forms I illustrated in Figs. 1 and 2.

In Fig.1 the arcs 11 and 12, or other sources of highfrequ'ency oscillations, are operatedfrom mains 13, 14: and 15, 16 respectively? These may connect either with a direct current source or an alteriiating' current source of relatively lowfrequency In order to prevent the high frequency ourrent from flowing through the source, ap-

propriate choke coils 17 and 18 may be provided in the mains. The arcs are enclosed in an atmosphere of hydrogen or other suitable gas, and operate inparallel to supply an antenna circuit comprising antenna 19, inductancc 20, and the ground 21. The invention, however, is fully as aaplicable to other forms of high frequency oad. Appropri-' ate means, such as electromagnets 22 and 23, are provided for influencing the operation of the arc in the ordinary manner.

' Included in each of the parallel or branch circuits is some form of reactor; in the form shown in Fig. 1 the condensers 24 and 25 are used. These condensers have reactances so chosen, so far as their relative values are concerned, as to cause the load to divide properly between the twopaths, and they are each great enough so that they form substantially all of the impedance in the path. Thus, if the condensers have reactances that are equal, then both branch circuits carry equal loads. If however, condenser 24 has twice the reactance of. contotal impedance of the circuit. The impede ance of the entire antenna circuit may be computed in the ordinary way, taking into conslderation the parallel paths through the arcs 11 and 12. The values chosen for the reactances of the condensers 24 and 25 are in a measure dependent upon the required value of the total impedance of the oscillatory circuit.

In addition to synchronizing the are currents and dividing the load roperly, it may be advisable to provide additional means to insure against cross currents between the arcs, or against tendency for the arcs to operate at any other frequency than that desired. Such a device is shown in the present instance at 26 and may consist of two balanced coils 27 ,and 28, one in eachbranch circuit, with a common iron core 29. This stabilizes the circuit in a manner described indetail in a copending application, Serial No. 527,885 in our names, entitled'Radio frequencysystem, filed concurrently herewith .and assigned to the same assignee .as the present invention. Other equivalent schemes therein described may' be utilized in lieu of that shown. In short, the arrangement is such that an increased energy loss results as soon as the desired condition of operation'is departed from. Thus, in the event of any cross currents, the coils 27 and 28, being so arranged that their magnetomotive forces add for cross currents, produce a strong field through the core 29. This causes a heavy core loss. For normal operation, the magnetic fields produced by the two coils substantially neutralize each other. Other conditions may be imposed, such as on the frequency, all as describedin the application heretofore identified.

Instead of utilizing capacitive reactances for the purpose of sychronizing and for dividing the load, it is possible to use inductive reactances. Such a scheme is shown in Fig. 2, wherein the inductors 30 and 31 are inserted in the branch circuits. \Vhen these inductors are used, it may become necessary to reduce the inductance 20 of the main oscillatory circuit to compensate for the high inductances of the two coils 30 and 31.

In addition to the coils 30 and 31, use may be made stopping condensers 32 and 33 in order to prevent interference between the sources of supply. An embodiment of the invention to a system utilizing a polyphase source for exciting the converters is illustrated in Fig. 3. In this case a three phase generator 34 of comparatively low frequency is arranged to supply three arcs 35, 36 and 37. These arcs are connected between the neutral point 38 of the generator 34, here shown as a Y connected machine, and the extremities of the three phases. Choke coils 39, 40 and'41 may be interposed between the arcs and the generator 34 for the usual purpose of preventing the flow of high frequency current through any of the phases of the generator. All the arcs are arranged in parallel to supply a load, such as the antenna load consistlng of the earth connection 21, inductor 20, and aerial 19. Inserted in each parallel path is a condenser 42, 43 or 44 which has a sufliciently high reactance to mask the impedance of the remainderof the circuit. As explained in connection with Fig. 1, this has the effect of ,three arcs, as well as of insuring pro r division of the load. This modification a so shows a stabilizing device between each pair of parallel circuits.- Thus the coils 45 and 46 have a common core 47 and serve to prevent cross currents between arcs 35 and 36. The branch circuits of thesev two arcs are united by conductor 47 connecting to a common point 48 in the antenna circuit. In an entirely similar manner, coils 49 and 50 stablize the circuit between parallel arcs 36 and 37, and the coils 51 and 52 stabilize the circuit between parallel arcs 35 and 37. It is thus seen that between each air of parallel arcs a stabilizing device is mserted, the

junction points of which are tied together at 48 to a point in the load circuit. The

scheme may be readily extended to any num-- A simplified scheme for t e operation of 3 three arcs in parallel s disclosed in- Fig. 4.

- In this figure the stabilizing devices between the-arcs are omitted, the effect of the condensers 42, 43 and 44; in the parallel circuit being proportioned so'as to make the use of further devices not absolutely essential.

It is furthermore not essential that .each arc should have a separate pair of electrodes.-

In the modification shown in Fig. 5, a com- I mon neutral electrode 53 is provided with which the three electrodes 54, 55 and 56 form the three arcs. Magnetic fields may be utilized in any appropriate manner to influence these arcs. In all other respects this figure is similar to Fig. 4;

A modified scheme for insuring load division is shown in Fig. 6. In this figure the parallel arcs 35, 36 and 37 are connected to a stabilizing device 56 which is shown diagrammatically. This device may comprise the sets of coils and cores shown in Fig. 3. In series with are 35 are the inductor 57 and condenser 60; in series with are 36, the in ductor 58 and condenser 61; in series with are 37 the inductor 59 and condenser 62.

In each arc circuit the condenser and induct-or are so. proportioned that at the desired frequency of operation, the combined reactance of these two elements is a minimum; in other words, the circuit is tuned to that frequency. In this instance, load division is secured by the proper choice of supply voltages and circuit resistances, which must have the proper relative values inthe various circuits. The stabilizing device 56, besides rendering the circuits stable, also synchronizes them, since when the circuits are not in synchronism, the magnetic balance is destroyed, in each pair of coils between the arcs out of synchronism.

The application of the last described scheme to a pair of arcs 11 and 12 operating in parallel. is illustrated in Fig. 7 In this figure the inductor 64 and condenser 63 in series with arc'llare tuned to resonance, as well as inductor 66 and condenser in series with the are 12. A stabilizing device to prevent cross currents is placed in circuit and is diagrammatically illustrated at 26. Here also, proper load division bet-ween the two arcs is assured by proper choice of operating voltages and by the resistances in each circuit, which form the total impedances of the assured by the action of the stabilizing device 26.

From the foregoing description, it is evident that we have provided novel and useful arrangements whereby arc converters may be efficiently operated in parallel.

I We claim:

1. In a radio frequency electrical system,

means-including a plurality of arcs 0perating in branch circuits forproducing high frequency oscillations, an impedance in series with each. arc of such value that it forms substantially all of the impedance in the branch circuit, and means for preventing cross currents between the arcs, comprlsing a device arranged to consume a substantial amount of energy when ([055 currents exist.

2. In a radio frequency electrical system, a plurality of means operating in parallel branch circuits, for producing high frequency oscillations, an impedance in each circuit of suclrvalue that it forms substantially all of the impedance in the circuit, and means for suming device consuming a substantial amount of energy upon the occurrence of cross currents.

4. In a radio frequency system, a plurality of means operating in parallel circuits for producing high frequency oscillations, an inductor and a condenser in series with each of said means, each of the parallel cir cuits being so tuned at the frequency-which 'it is desired to use that the total impedance in each of the circuits reduces merely to its resistance, and means for synchronizing the high frequency oscillations in the parallel circuits, comprising an energy consuming device, consuming a substantial amount of energy upon departure from synchronism.

5. In a radio frequency system having a plurality of parallel paths for the current flowing through the load, means for producing high frequency oscillations by an are located in one of the paths, an inductance coil in the same path as the are, another inductance coil in a path parallel to the are, .and a common core for these coils, the coils being so arranged that for an appreciable flow of current in a local circuit including the two coils, the core loss is considerable, while when the arc current flows entirely thpough the load, no appreciable core loss re su ts.

6. In a radiofrequency system, means for being. so arranged that for appreciable cross currents-between the arcs,-the core loss is considerable," while when there is no substantial cross current, no appreciable core loss results.

7. In a radio frequency system, a plurality of means for producing high frequency oscillations connected in parallel relation, an.

inductance coil in each of the parallel paths, and a common core for these coils, the coils being so arranged that for appreciable cross currents between the means, the core loss is considerable, while when there is no cross current, no appreciable core loss results.

8. In a radio frequency system, a plurality of are forming electrodes, means for supplying pairs of said electrodes with polyphase 15 current, whereby each pair operates on separate phases, a common oscillatory load circuit for all of the pairs of electrodes. and means for preventing cross currents between any of the arcs, comprising a pair of inductance coils for each pair of arcs, said inductance coils being located one in each of the two are circuits, and cores, one for each of said pairs of induction coils, said coils and cores being so arranged that an appreciable core loss results therein only when there are cross currents between the arcs.

In testimony whereof We have hereunto set our hands.

HAROLD F. ELLIOTT.

JAMES ARTHUR MILLER. 

